Sunday, May 30, 2021

Physics, Immortality, and the Afterlife

What does physics tell us about the possibility of immortality or an afterlife?

First, let’s address the elephant in the room.  To the physics community, “afterlife” often implies “religion” often implies “stupidity.”  Bullies like Richard Dawkins have made it very clear that anyone who even suggests the existence of God or an afterlife is intellectually inferior.  Oddly, this assertion directly conflicts with several arguments based on currently-understood physics (and often made, ironically, by atheists) that immortality is possible.  I’ll discuss below some of these arguments.  Importantly, any physicist who tells you with certainty that there is no afterlife is not only mistaken, but is ignorant of the direct logical implications of his/her own beliefs about physics.

Note: “Afterlife” and “immortality” are not technically the same.  Immortality might be interpreted as “never dying,” while an afterlife might be interpreted as “consciousness after one has died.”  However, from a physics standpoint, this is often a distinction without a difference.  For example, if mind uploading is possible, then it can be done before or after a person’s brain is dead.

Postponing Death

My close friend (and former MIT debate champion) once made the following (valid) argument:

·       Technology (e.g., medicine) is allowing humans to live longer and longer.

·       There is some tiny but nonzero probability 0<p<<1 that we will develop the technology to indefinitely postpone death.  For example, imagine that in the next 50 years we figure out how to make humans live to age 150, and in the following 50 years we figure out how to make humans live to age 200, and so on.  Then someone born today could indefinitely postpone death.

·       The universe will continue expanding forever.  (Most physicists believe that the universe has positive curvature.)

·       p * ∞ = ∞.

·       Therefore, the life expectancy of a person born today is infinite!

The argument applies equally to an afterlife as to immortality if we simply replace the second statement with “There is some tiny but nonzero probability 0<p<<1 that we will develop the technology to reanimate a dead person’s brain.”  (After all, that’s why the quacks at the Brain Preservation Foundation recommend cryogenic freezing of one’s brain, which I’m certain is not cheap.)  If we can agree that it is at least physically possible to indefinitely delay death (or to reanimate a dead brain), then physical immortality/afterlife cannot be ruled out.

Mind uploading

If you can upload your conscious awareness onto a computer, then you can live forever because a computer can be indefinitely operated and repaired.  Okay, okay, you still need energy to flow, which will stop when the universe experiences its predicted heat death in at least a googol years.  Even still, Michio Kaku in his fascinating book, Parallel Worlds, points out that conscious awareness would slow down commensurate with decreased energy transfer so that one’s subjective conscious experience wouldn’t notice.

Again, there’s no difference here between “immortality” and “afterlife” since the fundamental assumption of mind uploading (and algorithmic consciousness) is that a conscious state is just software running on a computer, and that can be done long after one’s death.  (It can also be done before one’s death, which leads to all kinds of ridiculous paradoxes that I discuss in this paper.) 

The problem is that I showed in this paper (and this) that consciousness is not algorithmic, which means it cannot be uploaded to or executed by a computer (whether digital or quantum).  Mind uploading is not physically possible.

Quantum Suicide

Max Tegmark, proponent of the wacky and unscientific Many Worlds Interpretation (“MWI”) of quantum mechanics, proposed the notion of quantum suicide (although really it’s just “quantum death” because it applies independently of intention) as an empirical test of MWI.  The idea is this:

·       Stand in front of a “quantum gun” that is designed so that when the trigger is pulled, whether a bullet actually fires from the gun (and kills you) depends on the outcome of a quantum mechanics (“QM”) event.

·       Universal linearity of QM – i.e., the assumption of U which I dispute here – implies that the quantum event entangles with the bullet, which entangles with you, to produce a Schrodinger’s-Cat-like state involving you in a superposition of states |dead> and |alive>. 

·       If MWI is correct, then both states actually occur/exist (albeit in different “worlds” that are exceedingly unlikely to quantum mechanically interfere).

·       Since you cannot consciously survive death – a huge assumption! – then the only state you can consciously observe is the one involving |alive>, which means that you are guaranteed to “survive” the pull of the quantum gun trigger.

·       You can repeat this as many times as you want, and every time you will be guaranteed to observe the outcome in which you are alive.

The argument is wrong for several reasons that I point out in the Appendix of this paper.  One problem is that every chance event is fundamentally (amplification of) a quantum event, which means that essentially every death-causing event is akin to quantum suicide/death.  But that means that, if Tegmark’s argument is correct, then nobody can actually die

But the main problem is that the argument depends on the unjustified and irrational assumption of U.  If Schrodinger’s Cat and Wigner’s Friend can’t exist, then the quantum suicide experiment can never get off the ground. 

Boltzmann Brain

The Boltzmann Brain concept is the notion that, given enough time, every physical state will repeat itself.  Or: due to random quantum fluctuations, given enough time, every possible physical configuration that can fluctuate into existence will fluctuate into existence.  So, eventually, even trillions of years after humanity has gone extinct, the conscious state you are experiencing at this moment will be recreated (and presumably re-experienced) again.  And again and again. 

Whether such experiences count as immortality or afterlife makes no difference, because the Boltzmann Brain concept is impossible.  I showed in this paper that physical instantiations of the same conscious state cannot exist at different points in spacetime. 

Tipler’s Physics of Immortality

Frank Tipler is a Christian who was largely ostracized from the academic world for showing how what is currently understood about physics could support the notions of a Christian God and afterlife.  His book, The Physics of Immortality, is interesting but dense.  At the risk of oversimplifying his analysis, I think his fundamental argument is really the Boltzmann Brain in disguise.  He relies heavily on the Bekenstein Bound (which I discussed here) and the notion of Eternal Recurrence to show that consciousness cannot end.

His analysis is wrong for several reasons.  First, the Bekenstein Bound assumes the constancy of the informational content in a given volume (i.e., that Planck’s constant is constant, which may be false).  Second, and more importantly, it assumes that a conscious state is just a list of numbers (even if it’s a huge list) that must be contained within the volume of a brain, and therefore that consciousness is algorithmic, which I’ve shown is false.  If consciousness cannot be reduced to a set of bits (and/or their algorithmic manipulation), then the number of bits that can fit in a given volume is irrelevant.


If physical systems are truly reversible, then – at least according to some – it should be possible in principle to physically reverse a person’s death (or even some or all of a person’s life).  It’s certainly not obvious that constantly “undoing” someone’s death results in a meaningful kind of immortality.  Still, maybe the goal of reversing someone’s death is to copy their consciousness into another physical system or upload it to a computer.  But I’ve already pointed out several times that this is impossible.  Either way, the entire argument is moot because physical reversibility of large systems is a logical contradiction.

What do I actually believe?

First, let me point out the crazy irony of this blog post so far.  I, the crackpot who believes in God, am trying to explain why several physicists’ arguments for immortality or afterlife are wrong!  In fact, the only one of the above arguments that I can’t completely rule out is Postponing Death, even though I regard it as extremely implausible to postpone death indefinitely.

Having said that, we do not understand consciousness.  No physicist, neurobiologist, physician, psychologist, computer scientist, philosopher, etc., understands consciousness, and anyone who claims to understand it is likely introducing unstated assumptions.  For example, most scientists who academically discuss consciousness assume that consciousness is created entirely by the brain, which is why the hackneyed “brain-in-a-vat” thought experiment – the namesake of this blog – is so pervasive in the literature. 

After all, if consciousness is entirely a product of the brain (or, more generally, on a local region of spacetime that may enclose the brain), then the above arguments are a lot more tenable.  That is, if a conscious state supervenes on a physical state that is entirely (locally) contained in some volume, then Tipler’s argument based on the Bekenstein Bound seems to apply; the total information specifying that conscious state is finite and, as nothing more than a string of numbers, can be copied and uploaded to a computer; and so forth.

In fact, given so many physical arguments for immortality, one might even wonder what physical arguments there are against immortality.  There is only one: assume that consciousness is entirely a product of the (living) brain; then death of the brain ends consciousness.  And if that assumption is wrong, then there is literally no existing scientific evidence against immortality or an afterlife.

But that assumption is wrong.  Conscious states are not local and they cannot be copied to different places in spacetime.  (Stoica makes a related and fascinating argument here that mental states are nonlocal.)  If they’re nonlocal, then they must physically depend on nonlocal (quantum) entanglements among objects and particles throughout the universe.  That is, what physically specifies my conscious state logically must extend beyond my brain.  There is certainly no doubt that my brain affects my consciousness, but it cannot be entirely locally responsible for it.  The fact that events and physical relationships that extend far beyond my brain are at least partially responsible for my consciousness leads me to surmise that these conscious-identity-producing physical relationships will persist long after the atoms in my brain are no longer arranged in their current configuration.  This is the beginning of an as-of-yet undeveloped physical argument for immortality/afterlife.

So, what do I really believe about an afterlife?  I won’t mince words.  I am certain that my consciousness is eternal; I am certain that my consciousness awareness will not permanently end if/when my brain dies.  In future posts, I will give logical and physical arguments to support these assertions, but I wanted first to devote a blog post to what currently-understood physics implies. 

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